The wall crab spiders (family Selenopidae), a member of a group of families collectively called crab spiders because of their laterigrade (forward-facing) legs. They also move much like crabs. This family consists of about 175 species in three genera, of which Selenops is the best known. The family is primarily tropical with the genus Anyphops confined to Sub-Saharan Africa and the genus Hovops confined to Madagascar. The spiders are very flat and are commonly found on walls or under rocks. They are quite agile and very difficult to capture. In addition their coloring makes them often quite difficult to see.